Nitride-based p-i-n bandpass photodetectors

Nitride-based p-i-n bandpass photodetectors with semitransparent Ni-Au electrodes were successfully fabricated and characterized. The photodetectors exhibit a 20-V breakdown voltage and a small dark current of 40 pA at 4-V reverse bias. It was found that spectral responsivity shows a narrow bandpass characteristics from 337 to 365 nm. Moreover, the peak responsivity was estimated to be 0.13 A/W at 354 nm, corresponding to a quantum efficiency of 44 %. The relatively high response at shorter wavelength is due to the unoptimized thickness of p-Al0.1Ga0.9N absorption layer. At low frequency, the noise of the photodetector is dominant by the 1/f-type noise. For our 330 x 330 mum(2) device, given a bias of -3.18 V, the corresponding noise equivalent power and normalized detectivity D* are calculated to be 5.6 x 10(-12) W and 3.34 x 10(11) cmHz(0.5)W(-1) respectively.